Quick action thermostat



April 28, 1942. R. F. BUTLER ETAL 2,281,021

QUICK ACTION THERMOSTAT Filed April 1, 1940 I if a? I 35 [7 i4 0 Z;\ J4 ji 2/ jg j z [6 l6 0 U/Zaer Way rie Z W F fly Patented Apr. 28, 1942 UNITED STATES PATENT OFFICE QUICK ACTION THEBMOSTAT Ralph F. Butler and Oliver D. Westerberg, Chicago, Ill.

Application April 1, 1940, Serial No. 321,214 2 Claims. .(Cl. 200-139) This invention relates to thermostats and more particularly thermostat, whereina spring snap arrangement is provided to causethe electrical contacts to open and close rapidly in response to the more slow and gradual movements of the temperature-sensitive actuating elements. 7

One of the principal objects of the invention is to provide a new and improved thermostat, so designed as tobe capable of unusual economical manufacture and convenient assembly, adapted to operate successfully within a relatively small range of temperatures between the opening and closing positions Another object of the invention is to provide a snap member consisting of a thin flat spring having pivotal edges at either end and mounted undena compression spring in slightly curved eral forces applied to the will readily cause it to snap ter to the other.

A further object of the invention is' to provide a snap member as described, interconnectedat its center pointto a gradual action thermostatic element by means of a lost-motion connection arranged to permit engagement or limited separation of the thermostat contacts. p

A further object of the invention is to provide a mounting bracket forthesnap action contactor, whereby the longitudinal compression stress on the contactor may be adjusted by equal and opposite movements of the opposite pivot sockets of the mounting bracket, to the end that the effective stress on the center of the spring from one side of cencontactor may be adjusted without altering the relative position of the electrical contacts secured. to the center point of the contactor.

Another object of the convenient adjusting means whereby the gradu- 211 action temperature-sensitive member may be moved into proper cooperating position with the contactor after each of these parts has been mounted in a common frame. I 7

Other objects will appear hereinafter.

Referring now more particularly to the drawing:

Fig. l is a front elevational view of a thermostat constructed in accordance with the principles of this invention illustrating the contacts in closed position;

Fig. 2 is a view similar to Fig. 1, illustrating the contacts in their open position; and

Fig. 3 is a detail sectional view taken substanthe line 3-3 in Fig. l.

tially on the plane of to the so-called quick action type of and stress sufficient to maintain the position, such that latinvention is to provide The frame of the thermostat comprises a channel member ID in which an insulating mounting strip II is secured by a plurality of eyelets l2. Perforations l3 and H are provided in order to permit the thermostat to be readily mounted and closely secured to electrical heating mechanism to control the temperature thereof,

The temperature-sensitive thermostatic element illustrated in the preferred embodiment of the invention consists of a Ushaped bi-metallic strip l5 rigidly mounted to the insulation strip H by a machine screw I6 clamped to the frame channel ID by the lock nuts I1, and insulated from the channel III by the shouldered insulating washer l6. The free end of the bi-metallic strip l6 carries a U-shaped saddle 2| to which an electrical contact are secured. The contact-22 is adapted to engage a cooperating contact 24 riveted to the midpoint of a flat leaf spring contactor or snap element 25. It will be noted that the distance between the insulating stop 23 and the contact 22 is greater than the thickness of the spring 26 and contact 24, and thusprovides a lost-motion connection, so that the contacts 22 and 24 may separate'a limited amount, after which the spring 26 will contact the insulating stop 23, thus preventing further separation of the contacts and limiting the movement of the spring. The spring 25 is provided at each of its extreme ends with sharp contacting edges 26 and 21 adapted to seat in pivot sockets 23 and 23 stamped in the arms 3| and 32 of the mounting bracket 33.

This mounting bracket 33 is preferably formed of a single strip of spring steel material shaped to provide a central portion 34 and a pair of curved fulcrum portions 35 and 36 between the central portion 34 and each of the aforementioned arms 3| and 32. It should be particularly noted that these fulcrums 3 5 and 36 are the only parts of the mounting bracket 33 coming in contact with the insulating strip II, with the result that any adjustment of the center portion 34 of the bracket will cause the arms 3| and 32 pivot about the fulcrums 36 and 36, respectivei and to simultaneously come together or separate. To aflord a convenient means of adjustment, an adjusting screw 4| is extended through a central perforation in the mounting bracket 33 and threaded into the insulating strip A pair of lock nuts 42 are provided to maintain the screw 4| in a predetermined set position and these lock nuts 42 are insulated from the frame channel II by a shouldered insulating washer 43.

It will be understood that the particular de- 22 and an insulating stop 23 between the pivot sockets 2i and 20, the contact 24 will be snapped quickly in the direction of movement. It will also be appreciated that the resilient nature of the mounting bracket 33 per.- mits a certain degree of flexing of the arms 3| and 32 and allows the snap action to be accomplished more smoothly and easily than if the pivot sockets 28 and 2! were solidly mounted.

To secure the most satisfactory operation of the thermostat, member 25 move equidistant on either side of the center line established between the pivot sockets 28 and 29, and it is, therefore, essential that the bi-metallic thermostatic element l5 be positioned so that its range of movement in the normal process of operation shall also be equidistant on either side of this center line. This is accomplished by the provision of an adjusting screw 44 threaded in the side wall of the channel It and adapted to be locked in predetermined'adjustment by the lock nut 45. An insulating cap 46 is provided to prevent electrical conduction between the screw 44 and the bi-metallic strip I 5.

Operation Assuming that the thermostat is in closed position, as illustrated in Fig. 1, there will be nov motion of parts until such time as the temperature rises and causes the bi-metallic element l5 to move the saddle 2| upwardly as viewed in the drawing. When this movement has continued sufficiently to straighten the spring 25 and move it slightly beyond the dead center position, the resiliency of the mounting bracket 33 will cause the spring 25 to snap upwardly to the position illustrated in Fig. 2, causing the contacts 22 and 24 to separate and interrupting the electrical circuit through the thermostat. It will be noted, however, that the movement of the spring 25 is limited by reason of the fact that it'will come into contact with the insulating stop 23, and since the movement of this spring is so small,-it will be readily appreciated that a slight decrease of the temperature of the thermostatic element l5 will cause the spring 25 to be again moved across cencontacting member,

it is desirable that the snap V ter in the opposite direction and to snap the contacts 24 and 22 into engagement and again complete the circuit. It is particularly important to note that the spring 25 is normally fiat and, therefore, affords no resistance to either direction of movement imparted by the bi-metallic strip I5, except such as may be due to the longitudinal compression stress exerted on the spring 25 by the mounting bracket 33. This permits an unusually free and positive operation of the conductor and minimizes the mechanical resistance which the conductor may offer to the movement of the .thermostatic strip.

While we have shown described the pres ent preferred embodiment of the present inventhe inventionspirit, and we, therefore, do not wish to be limited except as by the appended claims We claim:

1. In a thermostat, a snap action contactor as-- sembly comprising a flat spring snap member and portion, a pair of pivot sockets, and adjusting means to move each of said sockets equally and simultaneously in opposite directions; said snap member consisting of a narrow, thin, relatively long, normally flat spring including a pair of pivoting edges at the opposite ends and a central electrical contact; said contactor assembly being adapted to be actuated through an across-center toggle action by a relatively long gradual action, a U-shaped temperature-sensitive actuating member consisting of a bi-metallic strip includlimited separation of contacts responsive to relative movement in the opposite direction.

flange of the channel; a snap action contactor assembly mounted on one end of the block by a central through-bolt insulated from the frame;

said'assembly comprising a channel-shaped spring pivot sockets for snap cross-center motion; said contactor assembly being adapted for adjustment by said central bolt to move the pivot sockets equally and simultaneously in opposite directions to adjust the snap action of the spring; a temperature-sensitive actuating member consisting of a relatively long U-shaped bi-metallic strip mounted on the end of the insulator block by a through-bolt insulated from the frame; a lost motion clip mounted on the loose end of the strip frame with the insulated through-bolts providing outside electrical connector posts.

OLIVER D. WESTERBERG.

RALPH F. BUTLER. 

